SRP module documentation

Signed-off-by: Antoine Salon <asalon@vmware.com>

Reviewed-by: Paul Dale <paul.dale@oracle.com>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/7522)

2 files changed, 14 insertions, 9 deletions

diff --git a/crypto/srp/srp_lib.c b/crypto/srp/srp_lib.c
index b97d630d37..a9e244ea91 100644
--- a/crypto/srp/srp_lib.c
+++ b/crypto/srp/srp_lib.c
@@ -44,13 +44,13 @@ static BIGNUM *srp_Calc_xy(const BIGNUM *x, const BIGNUM *y, const BIGNUM *N)
 
 static BIGNUM *srp_Calc_k(const BIGNUM *N, const BIGNUM *g)
 {
-    /* k = SHA1(N | PAD(g)) -- tls-srp draft 8 */
+    /* k = SHA1(N | PAD(g)) -- tls-srp RFC 5054 */
     return srp_Calc_xy(N, g, N);
 }
 
 BIGNUM *SRP_Calc_u(const BIGNUM *A, const BIGNUM *B, const BIGNUM *N)
 {
-    /* k = SHA1(PAD(A) || PAD(B) ) -- tls-srp draft 8 */
+    /* u = SHA1(PAD(A) || PAD(B) ) -- tls-srp RFC 5054 */
     return srp_Calc_xy(A, B, N);
 }
 
@@ -254,13 +254,13 @@ static SRP_gN knowngN[] = {
 
 /*
  * Check if G and N are known parameters. The values have been generated
- * from the ietf-tls-srp draft version 8
+ * from the IETF RFC 5054
  */
 char *SRP_check_known_gN_param(const BIGNUM *g, const BIGNUM *N)
 {
     size_t i;
     if ((g == NULL) || (N == NULL))
-        return 0;
+        return NULL;
 
     for (i = 0; i < KNOWN_GN_NUMBER; i++) {
         if (BN_cmp(knowngN[i].g, g) == 0 && BN_cmp(knowngN[i].N, N) == 0)
diff --git a/crypto/srp/srp_vfy.c b/crypto/srp/srp_vfy.c
index 17b35c00f9..622fffbcd0 100644
--- a/crypto/srp/srp_vfy.c
+++ b/crypto/srp/srp_vfy.c
@@ -340,12 +340,13 @@ static SRP_gN *SRP_get_gN_by_id(const char *id, STACK_OF(SRP_gN) *gN_tab)
     int i;
 
     SRP_gN *gN;
-    if (gN_tab != NULL)
+    if (gN_tab != NULL) {
         for (i = 0; i < sk_SRP_gN_num(gN_tab); i++) {
             gN = sk_SRP_gN_value(gN_tab, i);
             if (gN && (id == NULL || strcmp(gN->id, id) == 0))
                 return gN;
         }
+    }
 
     return SRP_get_default_gN(id);
 }
@@ -374,9 +375,13 @@ static BIGNUM *SRP_gN_place_bn(STACK_OF(SRP_gN_cache) *gN_cache, char *ch)
 }
 
 /*
- * this function parses verifier file. Format is:
- * string(index):base64(N):base64(g):0
- * string(username):base64(v):base64(salt):int(index)
+ * This function parses the verifier file generated by the srp app.
+ * The format for each entry is:
+ * V base64(verifier) base64(salt) username gNid userinfo(optional)
+ * or
+ * I base64(N) base64(g)
+ * Note that base64 is the SRP variant of base64 encoding described
+ * in t_fromb64().
  */
 
 int SRP_VBASE_init(SRP_VBASE *vb, char *verifier_file)
@@ -605,7 +610,7 @@ char *SRP_create_verifier(const char *user, const char *pass, char **salt,
         g_bn = g_bn_alloc;
         defgNid = "*";
     } else {
-        SRP_gN *gN = SRP_get_gN_by_id(g, NULL);
+        SRP_gN *gN = SRP_get_default_gN(g);
         if (gN == NULL)
             goto err;
         N_bn = gN->N;